CPT Code


Specimen Type


Container Type

Blue-Sodium Citrate


Room Temperature, 4 hours; 2-8° C, 4 hours; -20°C, 2 weeks

Handling Instructions

Spin within 1 hour; Stored at RT

Clinical Notes

The partial thromboplastin time (PTT; also known as activated partial thromboplastin time (aPTT)) is a screening test that helps evaluate a person’s ability to appropriately form blood clots. It measures the number of seconds it takes for a clot to form in a sample of blood after substances (reagents) are added. The PTT assesses the amount and the function of certain proteins in the blood called coagulation or clotting factors that are an important part of blood clot formation.